Production of oils stable to ultra-violet light

ABSTRACT

LUBRICATING OILS STABLE TO ULTRA-VIOLET LIGHT AND HAVING IMPROVED COLOR AND VISCOSITY INDEX ARE PREPARED BY SEVERE HYDROGENATION, DEWAXING AND CLAY CONTACTING LUBRICATING OIL FRACTIONS.

United States Patent 3,684,684 PRODUCTION OF OILS STABLE TO ULTRA-VIOLET LIGHT Richard L. Coleman, Port Arthur, and Billy H. Cummins and William B. Ashton, Nederland, Tex., assignors to Texaco Inc., New York, N.Y. No Drawing. Filed Apr. 13, 1970, Ser. No. 27,978 Int. Cl. Cg 41/00, 23/02 US. Cl. 208-28 9 Claims ABSTRACT OF THE DISCLOSURE Lubricating oils stable to ultra-violet light and having improved color and viscosity index are prepared by severe hydrogenation, dewaxing and clay contacting lubricating oil fractions.

This invention relates to the production of improved petroleum oils. More particularly it is concerned with a process sequence for the production of base oils of high viscosity index having good stability towards ultraviolet light suitable for blending into multigrade lubricating oils, automatic transmission fluids and other specialty oils having a high viscosity index. In one of its more specific aspects, it is concerned with the production of high viscosity index lubricating oils of good color and ultraviolet stability from lubricating oil charge stocks using a process sequence which includes in a preferred embodiment hydrocracking, dewaxing and clay percolation.

Various steps for the refining of lubricating oils such as distillation, solvent refining, solvent dewaxing, acid treating and clay contacting are well known. When residual type oils are being processed, a preliminary step of deasphalting is also generally required.

In the processing steps listed above, distillation is employed as a means of separating a crude oil into fractions of various viscosities, solvent refining with, for example, furfural, sulfur dioxide or phenol is ordinarily used as a means of removing aromatic compounds and thereby improving the viscosity index, solvent dewaxing using for example a mixture of methyl ethyl ketone and toluene is used to improve low temperature properties by lowering the pour point of the oil and clay contacting is used generally as a final step to further improve the color and to neutralize the oil after it has been acid treated to improve color, oxidation and heat stability.

In a typical operation, a crude oil is topped under atmospheric pressure to produce light distillates and an atmospheric reduced crude which is then vacuum distilled to produce lube oil distillates with the residue from the vacuum distillation being deasphalted to yield residual lubricating stocks. conventionally, the various lube oil fractions are then further processed by solvent refining and dewaxing. With the advent of mild hydrogenation, acid treating and clay contacting have more or less fallen into disuse.

In conventional lube oil refining the solvent extraction step is carried out first to recover about 45-90% of the charge as solvent refined oil and to reject about 10-55% of the charge as dark colored, viscous extract. Since the extract amounts to a relatively high percentage of the charge and is not suitable for up-grading to a satisfactory quality level for use as a lube oil, solvent extraction has, up to the present been the most logical and economical step to apply first.

Because of the increasing demand for the lighter grade lubricating oils it has been found advantageous to convert the heavier oils to the more valuable lighter products by hydrocracking, or severe hydrotreating. Not only does this result in an increase in yield of desired lube oil fractions but because of the high hydrogen pressures involved ice which result in a reduction in the aromatic content of the oil, hydrocracking and hydrotreating have been proposed as replacements for solvent refining. However, for not completely known reasons, oils prepared by hydroprocessing are not stable to ultraviolet light, and form a flocculent precipitate upon exposure thereto.

It is therefore a principal object of this invention to improve the stability to ultraviolet light of oils produced by hydroprocessing. Another object is to improve the color of a hydroprocessed lube oil. Still another object is to produce a high viscosity index hydroprocessed oil while obtaining a product having an SUS viscosity of 3060 at 210 F.

According to our invention a petroleum oil is subjected to hydroprocessing to improve its viscosity index, is de- Waxed to lower its pour point and is clay percolated to improve its stability to ultraviolet light.

The process of the invention may be applied to a variety of feedstocks. For example, the feed may be obtained by subjecting a vacuum residuum to deasphalting with a low molecular weight hydrocarbon such as propane or butane. The deasphalted residuum can then be hydroprocessed. It is also possible to feed a wax distillate to the hydroprocessing stage. The feed whether obtained by vacuum distillation or by deasphalting a vacuum residuum may be subjected to a preliminary solvent refining before being subjected to hydroprocessing. It is also possible to use as the feed a lubricating oil fraction which has been obtained from a residuum such as atmospheric residuum or vacuum residuum by a simultaneous deasphalting-solvent refining procedure as disclosed in US. patent application Ser. No. 863,312, filed Oct. 2, 1969 and now abandoned in which the residuum is treated not with the conventional low molecular weight hydrocarbon deasphalting agents but with a solvent such as furfural or N-methyl-Z-pyrrolidone and the ralfinate of reduced aromatic and asphalt content is charged to the hydroprocessing zone.

The reaction conditions for the hydroprocessing may be varied depending on the product desired and on the charge stock. Typical reaction conditions include a temperature of about 700900 R, preferably 750-850 F. The hydrogen partial pressure may range between about 500 and 5000 p.s.i.g., a preferred range being from 1500 to 3000 p.s.i.g. Space velocities may vary between about 0.1 and 3.0 v./v./hr. with a preferred range being 0.2-1.0. Hydrogen rates of from LOGO-10,000 s.c.f.b-. have been found :atisfgctory although rates of 3000-7000 s.c.f.b. are preerre Hydrogen from any suitable source such as electrolytic hydrogen, hydrogen obtained from the partial combus tion of hydrocarbonaceous material followed by shift conversion and purification or catalytic reformer byproduct hydrogen may be used. The hydrogen should have a purity of between about 50 and 100% with by drogen purities of at least volume percent being preferred.

The oil and hydrogen ordinarily are preheated and brought into contact with a catalyst. The catalyst may be in the form of a fixed bed, a moving bed, a fluidized bed or may be slurried with the oil. In the case of a fixed bed, hydrogen flow may be upward or downward through the reactor as may "be the flow of the oil. In a specific embodiment, both the oil and a portion of the hydrogen are introduced at the top of a reactor con taining a fixed bed of the catalyst, the balance of the hydrogen being introduced at intermediate points in the reactor for cooling purposes.

The catalyst for the hydroprocessing step preferably comprises a compound of a Group VI metal such as molybdenum, chromium or tungsten or a compound of a Group VIII metal such as cobalt, iron or nickel and mixtures thereof. Ordinarily the catalyst is charged to the reactor in oxide from although it can be expected that some reduction and some sulfidation take place during the course of the process so that after being on stream for some time, the catalyst is probably a mixture of the metal, the metal sulfide and perhaps the oxide. If desired, the catalyst after being charged to the reactor but prior to the institution of the onstream period may be converted at least in part to the sulfide form for example by contact with a gas such as a mixture of hydrogen and sulfiding agent, e.g. hydrogen sulfide, methyl mercaptan or carbon disulfide. The Group VII metal may be present in an amount varying from 1 to 20% by weight of the total catalyst composite, preferably 2-15% and the Group VI metal may be present in an amount ranging from about 5-40%, preferably 7-25%. Preferred combinations are nickel tungsten, nickel molybdenum and cobalt molybdenum.

The hydrogenating component is supported on a refractory inorganic oxide such as hydrogen form or decationized zeolite Y, alumina, zirconia, silica or magnesia and mixtures thereof optionally prompted with an acidic material such as boron oxide or a halogen.

Advantageously, the catalyst has a surface area of at least 150 m. /g., a pour volume of at least 0.5 cc./ g. and an average pour diameter between 50 and 100 A. The upper limit of the surface area and pour volume is governed by the hardness and ruggedness of the catalyst. As a practical matter, for commercial installations Where the catalyst is used in units capable of processing several thousand barrels of charge per day, the surface area probably should not exceed about 800 m. g. and the pour volume should not exceed about 0.8 cc./g.

The catalyst may be prepared by any of the methods well known in the art, such as by impregnating the support with a solution of a salt of one of the metals, filtering, drying and then if desired impregnating with a solution of a salt of another metal, filtering, drying and calcining in a manner well known in the art.

The efiluent from the hydroprocessing is cooled and, in one embodiment of the invention, hydrogen-rich gas is separated therefrom and recycled to the hydroprocessing zone. Optionally, the hydrogen-rich stream is treated to remove any ammonia contained therein or a portion thereof may be bled from the system to prevent the build-up of ammonia and/or low molecular Weight hydrocarbons. Hydrogen is added to the recycle stream to replace that consumed in the hydroprocessing and if required to replace any hydrogen purged from the sys tem. Lubricating oil fractions are recovered from the balance of the eflluent by distillation, if necessary, at reduced pressure.

After hydroprocessing the oil is subjected to dewaxing to reduce its pour point. In one embodiment of our invention, the entire efiluent from the hydroprocessing zone is passed into contact with a catalyst comprising a hydrogenating component, such as is used in the hydroprocessing catalyst, supported on a decationized mordenite. Preferably the support is made by treating a synthetic mordenite with acid to replace the sodium ions with hydrogen ions.

Advantageously, the synthetic mordenite is treated with acid to the extent that a portion of he alumina is leached out to produce a mordenite having a silicazalumina mol ratio of at least 20 and having increased dewaxing activity. The catalytic dewaxing may be carried out at a temperature of at least 450 F., a pressure of at least 300 p.s.i.g., a space velocity of 0.2-5.0 v./-v./hr. and a hydrogen rate of 1000-10,000 s.c.f.b. Preferred conditions in the catalytic dewaxing zone are a temperature of 450-800 F., a pressure of 300-1500 p.s.i.g. and a space of velocity of 0.22.0.

Alternatively, the oil may be recovered from the hydroprocessing zone effluent and contacted with a dewaxing solvent such as a mixture containing 40-60 volume percent of a ketone such as acetone, methyl ethyl ketone or normal butyl ketone and 6040 volume percent of an aromatic compound such as benzene or toluene in a ratio of about 34 parts by volume of solvent per volume of oil, the mixture cooled to a temperature of about 0 to 20 F. and the waxy components removed by filtering or centrifuging. The filtrate is then subjected to flash distillation and stripping to remove the solvent.

The dewaxed oil is then clay percolated to improve its stability to ultraviolet light. This is effected by passing the oil through a column or adsorbent agent such as Fullers earth, Attapulgus clay, porocel clay, bauxite, silica or mixtures thereof referred to herein generically as clay. The flow through the column may be upward or downward, upward flow being preferred as there is less tendency toward channeling. The adsorbent may either be fresh or may have been used and regenerated by burning.

Operating conditions are a temperature of ambient to 200 F., a flow rate of 0.01 to 2.0 barrels of oil per ton of clay per hour and a total throughput of 10 to 200 barrels of oil per ton of clay. Preferred conditions are temperatures between ambient and 160 F., flow rates between 0.1 and 1.5 and throughputs of 30-150.

The following example is submitted for illustrative purposes only.

In this example the catalyst contains 2.3 wt. percent cobalt and 9.9 Wt. percent molybdenum, 4 wt. percent silica and the balance alumina. It has a surface area of 270 m. /g., a pour volume of 0.63 cc./g. and an average pore diameter of A. Data on the charge product and reaction conditions are tabulated below.

Propane deasphalted vacuum residuum from Mid-Continent Charge to hydrotreating: crude Charge tests:

Viscosity:

SUS/ F. 4381. SUS/210 F. 189. VI 82. Color, Lovi /2 inch 950. Carbon residue, wt. percent 1.9. Pour, F. Hydrotreating conditions:

Reactor temp., F 820.

Space velocity, Vo/hr./Vc .49.

Pressure, p.s.i.g. 1500.

Hydrogen rate, s.c.f.b. 5035. Dewaxing conditions:

Solvent dilution, volume 3.5: 1.0.

Wash solvent ratio, volume 1.0: 1.0.

Filtering temperature, F. -20.

Solvent composition:

Vol. percent methyl ethyl ketone 50. Vol. percent to1uene 50. Hydrotreated oil tests:

After solvent dewaxing to +5 F. pour: Viscosity:

SUS/100" F. 176.7 SUS/210 F. 45.6. Viscosity index 110.

UV. stability,

appearance after 112 hours Floc and haze. Clay percolation conditions:

Temperature, F. Ambient. Rate, b.p.t./hr .17.

See footnote at end of table.

Propane deasphalted vacuum residuum from Mid-Continent Charge to hydrotreating: crude Clay percolation conditions:

Throughput, b.p.t. 50. Clay Dried-reburned porocel. Percolated oil tests: Viscosity:

SUS/lOO" F. 173.1. SUS/2l0 F. 45.3. Viscosity index 107. 'U.V. stability, appearance after 112 hours Bright and clear.

1 Extrapoiated.

We claim:

1. A process for the production of a lubricating oil which consists essentially of in sequence deasphalting a crude oil vacuum residuum, contacting the deasphalted product in the presence of hydrogen with a catalyst comprising a Group VIII metal compound on an inorganic oxide support at a temperature between about 700 F. and 900 F. and a pressure between about 500 and 5000 p.s.i.g., subjecting the hydroprocessed product to dewaxing, passing the dewaxed oil through a bed of clay at a temperature between ambient and 160 F. and a flow rate between 0.1 and 1.5 barrels of oil per ton of clay per hour and recovering a lubricating oil product stable to ultraviolet light.

2. The process of claim 1 in which the dewaxing is eifected in the presence of hydrogen and a mordenite catalyst.

3. The process of claim 1 in which the dewaxing is effected by means of a solvent.

4. The process of claim 1 in which the residuum has 6 been deasphalted by means of a. low molecular weight hydrocarbon.

5. The process of claim 1 in which the residuum has been deasphalted by means of a solvent selected from the group consisting of furfural and N-methyl-2-pyrrolidone.

6. The process of claim 1 in which the catalyst has a surface area of at least 150 m. /g., a pore volume of at least 0.5 cc./g. and an average pore diameter of -100 A.

7. The process of claim 6 in which the surface area is between 250 and 800 m. /g., the pore volume is betwee 0.6 and 0.8 cc./g. and the average pore diameter is between and A.

8. The process of claim 1 in which the catalyst composition comprises an iron group metal compound and a Group VI metal compound and has a surface area of between 250 and 800 m. /g., a pore volume between 0.6 and 0.8 cc./g. and an average pore diameter between 75 and 95 A.

9. The process of claim 8 in which the lubricating oil fraction is a residuum which has been deasphalted by means of a solvent selected from the group consisting of furfural and N-methyl-Z-pyrrolidone.

References Cited UNITED STATES PATENTS 2,596,942 5/1952 Robertson et al. 208-26 3,080,313 3/1963 Beals et al 208---14 3,242,068 3/1966 Paterson 208-18 FOREIGN PATENTS 1,006,508 10/1965 Great Britain 208--18 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 208--18, 264 

